Electrochemical determination of bisphenol A in plastic bottled drinking water and canned beverages using a molecularly imprinted chitosan-graphene composite film modified electrode

Recent developments of (bio)-sensors for detection of main microbiological and non-biological pollutants in plastic bottled water samples: A critical review

The importance of water in all biological processes is undeniable. Ensuring access to clean and safe drinking water is crucial for maintaining sustainable water resources. To elaborate, the consumption of water of inadequate quality can have a repercussion on human health. Furthermore, according to the instability of tap water quality, the consumption rate of bottled water is increasing every day at the global level. Although most people believe bottled water is safe, it can also be contaminated by microbiological or chemical pollution, which can increase the risk of disease. Over the last decades, several conventional analytical tools applied to analyze the contamination of bottled water. On the other hand, some limitations restrict their application in this field. Therefore, biosensors, as emerging analytical method, attract tremendous attention for detection both microbial and chemical contamination of bottled water. Biosensors enjoy several facilities including selectivity, affordability, and sensitivity. In this review, the developed biosensors for analyzing contamination of bottled water were highlighted, as along with working strategies, pros and cons of studies. Challenges and prospects were also examined.

Mass Spectrometric Study of the Most Common Potential Migrants Extractible from the Inner Coatings of Metallic Beverage Cans

Population exposure to endocrine disrupting chemical- bisphenols, which are used commonly in food containers and drinking water pipes in Europe, is above acceptable health and safety levels, according to updated research data. In order to evaluate the most abundant potential migrants in canned sweetened beverages marketed in Poland, we performed the HPLC-MS screening test of the migrants present in the can coating material. The analyzed samples represented the three top-ranked companies of the global soft drink market; it is reasonable to assume that the obtained data are of global validity. The tested can coatings and beverages contained bisphenols conjugates such as five butoxyethanol (BuOEtOH) adducts with bisphenol A diglycidyl ether (BADGE), one butoxyethanol adduct with bisphenol A monoglycidyl ether (BAMGE), and cyclo-di-BADGE. The performed HPLC-MS/MS analysis in the MRM mode enabled evaluation of the concentrations of the detected conjugates in canned beverages which were found to be very low, namely at the level of 1 µg/L. On the other hand, the high consumption of canned beverages may yield a risk associated with the presence of these compounds in the diet. The subsequent HPLC-QTOF-MS/MS experiments allowed, for the first time, a detailed determination of the fragmentation pathways of the detected migrants as well as detection of the isomers of the two migrants, namely BADGE + BuOEtOH and BADGE + BuOEtOH + HCl.

An Overview to Molecularly Imprinted Electrochemical Sensors for the Detection of Bisphenol A

Bisphenol A (BPA) is an industrial chemical used extensively in plastics and resins. However, its endocrine-disrupting properties pose risks to human health and the environment. Thus, accurate and rapid detection of BPA is crucial for exposure monitoring and risk mitigation. Molecularly imprinted electrochemical sensors (MIES) have emerged as a promising tool for BPA detection due to their high selectivity, sensitivity, affordability, and portability. This review provides a comprehensive overview of recent advances in MIES for BPA detection. We discuss the operating principles, fabrication strategies, materials, and methods used in MIES. Key findings show that MIES demonstrate detection limits comparable or superior to conventional methods like HPLC and GC-MS. Selectivity studies reveal excellent discrimination between BPA and structural analogs. Recent innovations in nanomaterials, novel monomers, and fabrication techniques have enhanced sensitivity, selectivity, and stability. However, limitations exist in reproducibility, selectivity, and stability. While challenges remain, MIES provide a low-cost portable detection method suitable for on-site BPA monitoring in diverse sectors. Further optimization of sensor fabrication and characterization will enable the immense potential of MIES for field-based BPA detection.

Fabrication of a Molecularly-Imprinted-Polymer-Based Graphene Oxide Nanocomposite for Electrochemical Sensing of New Psychoactive Substances

As new psychoactive substances (commonly known as "the third generation drugs") have characteristics such as short-term emergence, rapid updating, and great social harmfulness, there is a large gap in the development of their detection methods. Herein, graphite oxide (GO) was first prepared and immobilized with a reversible addition-fragmentation chain transfer (RAFT) agent, then a new psychoactive substance (4-MEC) was chosen as a template, and then the surface RAFT polymerization of methacrylamide (MAAM) was carried out by using azobisisobutyronitrile (AIBN) as an initiator and divinylbenzene (DVB) as a cross-linker. After the removal of the embedded template, graphene oxide modified by molecularly imprinted polymers (GO-MIPs) was finally obtained. Owing to the specific imprinted cavities for 4-MEC, the satisfactory selectivity and stability of the GO-MIP nanocomposite have been demonstrated. The GO-MIP nanocomposite was then used to fabricate the electrochemical sensor, which displayed a high selectivity in detecting 4-MEC over a linear concentration range between 5 and 60 μg mL^-1 with a detection limit of 0.438 μg mL^-1. As a result, the GO-MIPs sensor developed an accurate, efficient, convenient, and sensitive method for public security departments to detect illicit drugs and new psychoactive substances.

An advantageous application of molecularly imprinted polymers in food processing and quality control

In the global market era, food product control is very challenging. It is impossible to track and control all production and delivery chains not only for regular customers but also for the State Sanitary Inspections. Certified laboratories currently use accurate food safety and quality inspection methods. However, these methods are very laborious and costly. The present review highlights the need to develop fast, robust, and cost-effective analytical assays to determine food contamination. Application of the molecularly imprinted polymers (MIPs) as selective recognition units for chemosensors' fabrication was herein explored. MIPs enable fast and inexpensive electrochemical and optical transduction, significantly improving detectability, sensitivity, and selectivity. MIPs compromise durability of synthetic materials with a high affinity to target analytes and selectivity of molecular recognition. Imprinted molecular cavities, present in MIPs structure, are complementary to the target analyte molecules in terms of size, shape, and location of recognizing sites. They perfectly mimic natural molecular recognition. The present review article critically covers MIPs' applications in selective assays for a wide range of food products. Moreover, numerous potential applications of MIPs in the food industry, including sample pretreatment before analysis, removal of contaminants, or extraction of high-value ingredients, are discussed.

A Status Update on the Development of Polymer and Metal-Based Graphene Electrochemical Sensors for Detection and Quantitation of Bisphenol A

The detection and quantitation of bisphenol A (BPA) in the environment and food products has been a subject of considerable interest. BPA, a diphenylmethane derivative is a well-known industrial raw material with wide range of applications. It is a well-known endocrine disruptor and acts as an estrogen mimic. BPA is an environmental health concern and its accumulation in hydro-geological cycles is a matter of serious ecological peril. This review basically assesses various chemically modified electrodes composed of diverse components that have been employed to recognize BPA in different matrices. Electrochemical sensors prepared using graphene materials in combination with metals and polymers for selective detection of BPA have been discussed extensively. The emphasis is on detection of BPA in various samples encountered in routine use such as plastic bottles, receipts, baby feed bottles, milk samples, mineralized water, tissue paper, DVDs, and others. Although research in this field is in the exploratory stage, deeper insights into fundamental studies of sensing systems, fast analysis of real samples and validation of sensors are some of the factors that need major impetus. It is expected that chemically modified electrode-based sensing systems will soon take over as a viable option for monitoring diverse pollutants.

Recent Advances of Nanomaterials-Based Molecularly Imprinted Electrochemical Sensors

Molecularly imprinted polymer (MIP) is illustrated as an analogue of a natural biological antibody-antigen system. MIP is an appropriate substrate for electrochemical sensors owing to its binding sites, which match the functional groups and spatial structure of the target analytes. However, the irregular shapes and slow electron transfer rate of MIP limit the sensitivity and conductivity of electrochemical sensors. Nanomaterials, famous for their prominent electron transfer capacity and specific surface area, are increasingly employed in modifications of MIP sensors. Staying ahead of traditional electrochemical sensors, nanomaterials-based MIP sensors represent excellent sensing and recognition capability. This review intends to illustrate their advances over the past five years. Current limitations and development prospects are also discussed.

Direct nitrogen interception from chitin/chitosan for imidazo[1,5-a]pyridines

A catalyst-free one-pot methodology that enables direct nitrogen interception of chitosan/chitin for imidazo[1,5-a]pyridines was developed. This strategy features direct synthesis of important deuterated imidazo[1,5-a]pyridines and tridentate ligands. In particular, a broad group of previously inaccessible products including saturated 1-alkylimidazo[1,5-a]pyridines are unprecedently synthesized by this protocol.

Migration of bisphenol A and its related compounds in canned seafood and dietary exposure estimation

The present study sought to investigate the migration of target bisphenols, such as BPA, BPF, BADGE, BADGE·H2O, BADGE·2H2O, and BFDGE in 102 samples of several canned seafood, namely canned Antarctic krill, scallop, oysters, mussel, clam, and mantis shrimp stored for months at different temperatures through a high-performance liquid chromatographic-fluorescence detector (HPLC-FLD) combined with a microwave-assisted extraction method. Except for BFDGE, the other five bisphenols were observed in most of the analyzed samples. The canned shrimp showed the highest migration of BPA (0.089 mg/kg), exceeding the specific migration limit (SML) of BPA (0.05 mg/kg) specified by the European Union (EU), while the migration levels of BADGE and its derivatives were within their SMLs. The migration behavior of bisphenols in the canned seafood was majorly affected by the analytes, storage conditions, and food types. BPA, BADGE·H2O, and BADGE·2H2O were characterized by a rapid migration during the first half of the shelf life, which increased with the increase of temperature, followed by a stabilization or decline of their concentrations for prolonged durations. Besides, the migration of target bisphenols was significantly influenced by the storage temperature in some seafood species. Notably, higher migration level of BPA was found in samples with higher fat content. The average dietary exposure of Chinese adults to BPA, BPF, BADGE·2H2O, BADGE·H2O, and BADGE of canned seafood was estimated at 11.69, 1.21, 6.47, 8.74, and 4.71 ng/kg bw/day, respectively. The target hazard quotient (THQ) values of all the analyzed bisphenols were below 1 for the Chinese adults, suggesting an insignificant exposure to these bisphenols through canned seafood consumption.

Antioxidant analysis of ultra-fast selectively recovered 4-hydroxy benzoic acid from fruits and vegetable peel waste using graphene oxide based molecularly imprinted composite

Food processing industries generate 25-30% of fruit and vegetable peel (F&VP) waste of the total produce, which are rich in polyphenolic antioxidants (PA). Sustainable solution for the above waste can be its valorization for the recovery of PA, often used as natural preservative. Present work reports rationally designed graphene oxide-based molecularly imprinted composites (GOMIPs) using ionic liquid 1-allyl-3-octylimidazolium chloride (A) as a green functional monomer for selective recovery of PA 4-Hydroxy benzoic acid (4HA) from F&VP/pomegranate peel (PGP) waste. GOMIP-A and GOMIP-V were characterized using various techniques for its successful synthesis. GOMIP-A attained equilibrium within 10 min with adsorption capacity of 190.56 μmol g-1 for 4HA. Developed HPLC method depicted selective recovery of 77.23% and 62.83% 4HA from F&VP and PGP waste respectively by GOMIP-A. Subsequently, desorbed 4HA from GOMIP-A matrices exhibited the antioxidant potential of 33.53% (F&VP extract) and 47.97% (PGP extract) for DPPH radical.

Molecularly Imprinted Polymers (MIPs) in Sensors for Environmental and Biomedical Applications: A Review

Molecular imprinted polymers are custom made materials with specific recognition sites for a target molecule. Their specificity and the variety of materials and physical shapes in which they can be fabricated make them ideal components for sensing platforms. Despite their excellent properties, MIP-based sensors have rarely left the academic laboratory environment. This work presents a comprehensive review of recent reports in the environmental and biomedical fields, with a focus on electrochemical and optical signaling mechanisms. The discussion aims to identify knowledge gaps that hinder the translation of MIP-based technology from research laboratories to commercialization.

Analysis of imidacloprid residues in mango, cowpea and water samples based on portable molecular imprinting sensors

Imidacloprid is a neonicotinoid insecticide widely used in the production and cultivation of crops. In recent years, the extensive use of imidacloprid in agricultural production has resulted in large amounts of pesticide residues in agricultural products and the environment. Therefore, it is necessary to establish a rapid, accurate, sensitive and convenient method for detecting imidacloprid pesticide residues to ensure the safety of agricultural products and the environment. To clarify how to use the molecular imprinting method for the electrochemical rapid residue detection of imidacloprid. This paper selected reduced graphene oxide and gold nanoparticles as modifiers modified on screen-printed carbon electrodes (SPCE) chitosan as a functional monomer, and imidacloprid as template molecule to prepare molecularly imprinted polymer, and applied this sensor to the residue detection of imidacloprid. The results showed that the concentration of imidacloprid showed a good linear relationship with the peak response current, and the detection limit of imidacloprid was 0.5 μM, while the sensor had good repeatability and interference resistance. The recoveries of imidacloprid spiked on three samples, mango, cowpea and water, were in the range of 90-110% (relative standard deviation, RSD<5%), which proved the practicality and feasibility of the assay established in this paper. The results of this paper can be used as a basis for the research on the detection of imidacloprid pesticide residues in food or environment.

Molecularly Imprinted Polymers Combined with Electrochemical Sensors for Food Contaminants Analysis

Detection of relevant contaminants using screening approaches is a key issue to ensure food safety and respect for the regulatory limits established. Electrochemical sensors present several advantages such as rapidity; ease of use; possibility of on-site analysis and low cost. The lack of selectivity for electrochemical sensors working in complex samples as food may be overcome by coupling them with molecularly imprinted polymers (MIPs). MIPs are synthetic materials that mimic biological receptors and are produced by the polymerization of functional monomers in presence of a target analyte. This paper critically reviews and discusses the recent progress in MIP-based electrochemical sensors for food safety. A brief introduction on MIPs and electrochemical sensors is given; followed by a discussion of the recent achievements for various MIPs-based electrochemical sensors for food contaminants analysis. Both electropolymerization and chemical synthesis of MIP-based electrochemical sensing are discussed as well as the relevant applications of MIPs used in sample preparation and then coupled to electrochemical analysis. Future perspectives and challenges have been eventually given.

A Review of Nanocomposite-Modified Electrochemical Sensors for Water Quality Monitoring

Electrochemical sensors play a significant role in detecting chemical ions, molecules, and pathogens in water and other applications. These sensors are sensitive, portable, fast, inexpensive, and suitable for online and in-situ measurements compared to other methods. They can provide the detection for any compound that can undergo certain transformations within a potential window. It enables applications in multiple ion detection, mainly since these sensors are primarily non-specific. In this paper, we provide a survey of electrochemical sensors for the detection of water contaminants, i.e., pesticides, nitrate, nitrite, phosphorus, water hardeners, disinfectant, and other emergent contaminants (phenol, estrogen, gallic acid etc.). We focus on the influence of surface modification of the working electrodes by carbon nanomaterials, metallic nanostructures, imprinted polymers and evaluate the corresponding sensing performance. Especially for pesticides, which are challenging and need special care, we highlight biosensors, such as enzymatic sensors, immunobiosensor, aptasensors, and biomimetic sensors. We discuss the sensors' overall performance, especially concerning real-sample performance and the capability for actual field application.

Construction of natural polymeric imprinted materials and their applications in water treatment: A review

Molecularly imprinted materials (MIMs) have been widely used in various fields, including water treatment, chemical sensing, and biotechnology, because of their specific recognition and high selectivity. MIMs are usually obtained via two successive steps, namely, (1) copolymerization and crosslinking reactions of the preassembled complex of comonomers and a specific target compound (2) and thorough removal of template molecules. Some functional polymers are directly used as supporting materials and functional groups assembled with target compound are provided to simplify the preparation of MIMs. Natural polymers, such as chitosan, cyclodextrin, sodium alginate, starch, cellulose, lignin and their derivatives, are good candidates because of their environmentally friendly properties, low costs, and abundant active functional groups. In this study, different methods for the preparation of natural polymeric MIMs were reviewed in terms of the construction of microscopic binding cavities and macroscopic visible condensed structures with different shapes. Natural polymeric MIMs in water treatment applications, such as adsorption and detection of various pollutants from aqueous solutions, were summarized. Prospects on the development of novel and high-performance natural polymeric MIMs were discussed to overcome the difficulties in their preparation and applications.

Latest Advances in Determination of Bisphenols with Nanomaterials, Molecularly Imprinted Polymers and Aptamer Based Electrochemical Sensors

Contamination of environmental sources such as soils, sediments and rivers and human exposure caused by several endocrine disrupting compounds (EDCs) are considered as the most challenging issues of today's world. EDCs cover a wide variety of compounds ranging from phthalates to parabens and bisphenols (BPs) are the leading group among them. BPs are widely used during the production of different plastic materials such as food and beverage containers, toys, medical equipment and baby bottles that we use in every aspect of our lives. BPs may migrate from those products to different media under certain conditions and this situation causes chronic exposure for humans and other creatures in the environment. Especially bisphenol A (BPA) and its other analogues such as bisphenol F, bisphenol S and tetrabromobisphenol that have similar structures and are preferred as alternatives to BPA cause harmful adverse effects such as endocrine disruption, neurotoxicity, genotoxicity and cytotoxicity. There are legal restrictions and prohibitions by the European Union (EU) in order to prevent possible harmful effects. Therefore, it is important to develop highly sensitive, fast, easy to use and cheap sensors for the determination of BPs in biological, environmental and commercial samples. Electrochemical sensors, which are one of the most widely, used analytical techniques, provide these conditions. Additionally, it is possible to enhance the performance of electrochemical sensors with nanomaterials, molecularly imprinted polymers or aptamer based technologies. This review aims to give comprehensive information about BPs with summarizing most recent applications of electrochemical sensors for their determination in different samples.

A green molecular imprinted solid-phase extraction protocol for bisphenol A monitoring with HPLC-UV to guarantee the quality and safety of walnuts under different storage conditions

Monitoring the residual toxicant concentrations in foods is the key step for minimizing potential hazards. The huge interest about food contamination and exposure to endocrine disruptors such as bisphenol A has emerged the development of sensitive analytical methodologies to guarantee the safety and quality of foods. In this work, a green molecularly imprinted solid-phase extraction protocol coupled with high-performance liquid chromatography with UV detection was optimized following the principles of green analytical chemistry. An imprinted sol-gel silica-based hybrid inorganic-organic polymeric sorbent was used to monitor the leaching of bisphenol A from different packaging materials (glass vessels, cans, and polypropylene containers) in walnuts stored within a period of 6 months at 25 and 4°C. Extraction parameters including loading time (5-20 min), solvent type (acetonitrile, ethanol, methanol, acetone, acetonitrile:methanol, 50:50, v/v), and elution flow rate (0.2-1 mL/min) were optimized with one-factor-at-a-time method. The selected extraction optimum parameters incorporated elution with acetonitrile at 0.2 mL/min flow rate, for 10 min sample holding time. The imprinting factor was equal to 4.55 ± 0.26 (n = 3). The optimized method presented high recovery (94.3 ± 4.2%, n = 3), good linearity (>0.999), intra-assay repeatability (90.2-95.6%, n = 3), and interassay precision (86.7-93.1%, n = 3).

Recent Advances in Electrochemical Sensors and Biosensors for Detecting Bisphenol A

In recent years, several studies have focused on environmental pollutants. Bisphenol A (BPA) is one prominent industrial raw material, and its extensive utilization and release into the environment constitute an environmental hazard. BPA is considered as to be an endocrine disruptor which mimics hormones, and has a direct relationship to the development and growth of animal and human reproductive systems. Moreover, intensive exposure to the compound is related to prostate and breast cancer, infertility, obesity, and diabetes. Hence, accurate and reliable determination techniques are crucial for preventing human exposure to BPA. Experts in the field have published general electrochemical procedures for detecting BPA. The present timely review critically evaluates diverse chemically modified electrodes using various substances that have been reported in numerous studies in the recent decade for use in electrochemical sensors and biosensors to detect BPA. Additionally, the essential contributions of these substances for the design of electrochemical sensors are presented. It has been predicted that chemically modified electrode-based sensing systems will be possible options for the monitoring of detrimental pollutants.

Nanotechnology-based approaches for food sensing and packaging applications

The rapid advancement of nanotechnology has provided opportunities for the development of new sensing and food packaging solutions, addressing long-standing challenges in the food sector to extend shelf-life, reduce waste, assess safety and improve the quality of food. Nanomaterials can be used to reinforce mechanical strength, enhance gas barrier properties, increase water repellence, and provide antimicrobial and scavenging activity to food packaging. They can be incorporated in chemical and biological sensors enabling the design of rapid and sensitive devices to assess freshness, and detect allergens, toxins or pathogenic contaminants. This review summarizes recent studies on the use of nanomaterials in the development of: (1) (bio)sensing technologies for detection of nutritional and non-nutritional components, antioxidants, adulterants and toxicants, (2) methods to improve the barrier and mechanical properties of food packaging, and (3) active functional packaging. The environmental, health and safety implications of nanomaterials in the food sector, along with an overview of regulation and consumer perception is also provided.

Recent Trends in the Analysis of Chemical Contaminants in Beverages

Chemical contaminants should not be present in beverages for human consumption, but could eventually be ingested by consumers as they may appear naturally from the environment or be produced by anthropogenic sources. These contaminants could belong to many different chemical sources, including heavy metals, amines, bisphenols, phthalates, pesticides, perfluorinated compounds, inks, ethyl carbamate, and others. It is well known that these hazardous chemicals in beverages can represent a severe threat by the potential risk of generating diseases to humans if no strict quality control is applied during beverages processing. This review compiles the most updated knowledge of the presence of potential contaminants in various types of beverages (both alcoholic and non-alcoholic), as well as in their containers, to prevent undesired migration. Special attention is given to the extraction and pre-concentration techniques applied to these samples, as well as to the analytical techniques necessary for the determination of chemicals with a potential contaminant effect. Finally, an overview of the current legislation is carried out, as well as future trends of research in this field.

Preparation and applications of electrochemical chemosensors based on carbon-nanomaterial-modified molecularly imprinted polymers

The past few decades have witnessed a rapid development in electrochemical chemosensors (ECCSs). The integration of carbon nanomaterials (CNMs) and molecularly imprinted polymers (MIPs) has endowed ECCSs with high selectivity and sensitivity toward target detection. Due to the integrated merits of MIPs and CNMs, CNM-modified MIPs as ECCSs have been widely reported and have excellent detection applications. This review systematically summarized the general categories, preparation strategies, and applications of ECCSs based on CNM-modified MIPs. The categories include CNM-modified MIPs often hybridized with various materials and CNM-encapsulated or CNM-combined imprinting silica and polymers on working electrodes or other substrates. The preparation strategies include the polymerization of MIPs on CNM-modified substrates, co-polymerization of MIPs and CNMs on substrates, drop-casting of MIPs on CNM-modified substrates, self-assembly of CNMs/MIP complexes on substrates, and so forth. We discussed the in situ polymerization, electro-polymerization, and engineering structures of CNM-modified MIPs. With regard to potential applications, we elaborated the detection mechanisms, signal transducer modes, target types, and electrochemical sensing of targets in real samples. In addition, this review discussed the present status, challenges, and prospects of CNM-modified MIP-based ECCSs. This comprehensive review is desirable for scientists from broad research fields and can promote the further development of MIP-based functional materials, CNM-based hybrid materials, advanced composites, and hybrid materials.

Selective electrochemical detection of bisphenol A using a molecularly imprinted polymer nanocomposite

A molecularly imprinted nanocomposite with covalently connected polyacrylate, β-cyclodextrin and graphene is synthesized for selective capture and electrochemical detection of bisphenol A.

Chemical and Biological Sensors for Food-Quality Monitoring and Smart Packaging

The growing interest in food quality and safety requires the development of sensitive and reliable methods of analysis as well as technology for freshness preservation and food quality. This review describes the status of chemical and biological sensors for food monitoring and smart packaging. Sensing designs and their analytical features for measuring freshness markers, allergens, pathogens, adulterants and toxicants are discussed with example of applications. Their potential implementation in smart packaging could facilitate food-status monitoring, reduce food waste, extend shelf-life, and improve overall food quality. However, most sensors are still in the development stage and need significant work before implementation in real-world applications. Issues like sensitivity, selectivity, robustness, and safety of the sensing materials due to potential contact or migration in food need to be established. The current development status of these technologies, along with a discussion of the challenges and opportunities for future research, are discussed.

In Situ Determination of Bisphenol A in Beverage Using a Molybdenum Selenide/Reduced Graphene Oxide Nanoparticle Composite Modified Glassy Carbon Electrode

Due to the endocrine disturbing effects of bisphenol A (BPA) on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode (GCE) modified with molybdenum selenide/reduced graphene oxide (MoSe₂/rGO) was fabricated for in situ determination of bisphenol A in several beverages. The surface area of the electrode dramatically increases due to the existence of ultra-thin nanosheets in a flower-like structure of MoSe₂. Adding phosphotungstic acid in the electrolyte can significantly enhance the repeatability (RSD = 0.4%) and reproducibility (RSD = 2.2%) of the electrode. Under the optimized condition (pH = 6.5), the linear range of BPA was from 0.1 μM⁻100 μM and the detection limit was 0.015 μM (S/N = 3). When using the as-prepared electrode for analyzing BPA in beverage samples without any pretreatments, the recoveries ranged from 98⁻107%, and the concentrations were from below the detection limit to 1.7 μM, indicating its potential prospect for routine analysis of BPA.

Study on the effect of graphene and glycerol plasticizer on the properties of chitosan-graphene nanocomposites via in situ green chemical reduction of graphene oxide

Unplasticized and glycerol plasticized chitosan/graphene (CS/GS) nanocomposites were synthesized via in situ chemical reduction of graphene oxide sheets (GO) with l-ascorbic acid (L-AA) as reductant by solution casting. The reduction of GO with L-AA was investigated to establish the optimal amount of reductant required to produce chemically reduced graphene sheets (GS). The combine effect of both nanofiller and glycerol on the structure, thermal, mechanical, and electrical properties of CS/GS nanocomposite films was evaluated. Materials were characterized by FT-IR, NMR, UV-Vis, XPS, XRD, Raman, SEM, TEM, and TGA. The results showed that GS sheets were homogeneously dispersed throughout the CS matrix, and that interactions between CS and the surface of GS took place. When compared with neat CS, nanocomposites showed a decrease in the crystallinity, better thermal stability under oxidative atmosphere, and improved mechanical properties, while maintained the thermal properties of CS under inert conditions. Combined use of glycerol and GS led to substantially enhanced mechanical properties. The electrical conductivity was increased with increasing GS loading in nanocomposite. This study demonstrates how CS/GS nanocomposites performance properties can be tailored by controlling GsS and plasticizer content.

Current Progress of Nanomaterials in Molecularly Imprinted Electrochemical Sensing

Nanomaterials have received much attention during the past decade because of their excellent optical, electronic, and catalytic properties. Nanomaterials possess high chemical reactivity, also high surface energy. Thus, provide a stable immobilization platform for biomolecules, while preserving their reactivity. Due to the conductive and catalytic properties, nanomaterials can also enhance the sensitivity of molecularly imprinted electrochemical sensors by amplifying the electrode surface, increasing the electron transfer, and catalyzing the electrochemical reactions. Molecularly imprinted polymers that contain specific molecular recognition sites can be designed for a particular target analyte. Incorporating nanomaterials into molecularly imprinted polymers is important because nanomaterials can improve the response signal, increase the sensitivity, and decrease the detection limit of the sensors. This study describes the classification of nanomaterials in molecularly imprinted polymers, their analytical properties, and their applications in the electrochemical sensors. The progress of the research on nanomaterials in molecularly imprinted polymers and the application of nanomaterials in molecularly imprinted polymers is also reviewed.

Advances in sensing and biosensing of bisphenols: A review

Bisphenols (BPs) are well known endocrine disrupting chemicals (EDCs) that cause adverse effects on the environment, biotic life and human health. BPs have been studied extensively because of an increasing concern for the safety of the environment and for human health. They are major raw materials for manufacturing polycarbonates, thermal papers and epoxy resins and are considered hazardous environmental contaminants. A vast array of sensors and biosensors have been developed for the sensitive screening of BPs based on carbon nanomaterials (carbon nanotubes, fullerenes, graphene and graphene oxide), quantum dots, metal and metal oxide nanocomposites, polymer nanocomposites, metal organic frameworks, ionic liquids and molecularly imprinted polymers. This review is devoted mainly to a variety of sensitive, selective and reliable sensing and biosensing methods for the detection of BPs using electrochemistry, fluorescence, colorimetry, surface plasmon resonance, luminescence, ELISAs, circular dichroism, resonance Rayleigh scattering and adsorption techniques in plastic products, food samples, food packaging, industrial wastes, pharmaceutical products, human body fluids and many other matrices. It summarizes the advances in sensing and biosensing methods for the detection of BPs since 2010. Furthermore, the article discusses challenges and future perspectives in the development of novel sensing methods for the detection of BP analogs.